I really like your point about voting not resulting in policy, I'd completely forgotten about that study and will be using it. But I'd like to clarify something:

a single vote is not going to make a difference

it's true that leftists are too small in number to sway an election

It doesn't matter if you're liberal or conservative or a leftist any single vote doesn't matter because single votes do not typically determine elections. Like you can be a liberal in a conservative area you'll be out voted or a liberal in a liberal area will likely have their candidate win by a significant margin meaning their vote didn't really matter either.